1. Field of the Invention
The present invention relates to a passenger detection system, and relates in particular to an improved passenger detection system that places the side airbag for the passenger, in the deployable or non-deployable state, depending on the seating conditions of the passenger (here, the term passenger also includes the driver) sitting in the driver's seat or front passenger's seat in an automobile.
This application is based on Patent Application No. Hei 10-257122, filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In general, an airbag apparatus in an automobile is aimed at protecting passenger(s) in the automobile from shocks, in the event of a collision, and is now considered to be an essential item for automotive safety, and in recent years, airbags have been provided for the front passenger's seat as well as for the driver's seat.
An example of such an airbag apparatus is shown in FIG. 12, and is comprised by: a driver-side squib circuit comprised by a series circuit including safety sensor SS1, squib SQ1, and a semiconductor switching device SW1 such as a field effect transistor; a front-passenger-side squib circuit comprised by a safety sensor SS2, a squib SQ2, and a semiconductor switching device SW2 such as a field effect transistor; an electronic accelerometer (impact sensor) GS; and a control circuit CC for judging presence/absence of an impact on the basis of output signals from the sensor GS, and supplying signals to the gate circuits of the switching devices SW1, SW2.
In this air bag apparatus, when a (substantial) head-on collision occurs for whatever reason, safety sensors SS1 and SS2 are closed responding to a relatively minor acceleration, and the squib circuits are placed in an operable state. And, when the control circuit CC judges that a collision has definitely taken place according to the signals from the accelerometer GS, signals are sent to the gates of switches SW1, SW2 and the switches SW1, SW2 are closed. As a result of a current flowing in the respective squib circuits, the driver-side and passenger-side airbags are immediately deployed because of the heating in the squibs SQ1 and SQ2, and the occupants are protected from the collision impact.
There are the following types of automobile collision: the first type in which both automobiles crash into each other head-on, the second type in which one automobile crashes into the side of another automobile, the third type in which one automobile crashes into the back of another automobile, and the like. Recently, an airbag apparatus as shown in FIG. 13 has been proposed for protecting passengers in the above second mode.
This airbag apparatus is made by adding a side airbag (apparatus) SA to the airbag apparatus shown in FIG. 12, and the basic structure of the airbag apparatus of FIG. 13 is the same as that of the airbag apparatus of FIG. 12.
That is, the side airbag apparatus SA is comprised by: a driver-side squib circuit comprised by a series circuit including safety sensor SS3, squib SQ3, and a semiconductor switching device SW3 such as a field effect transistor; and a front-passenger-side squib circuit comprised by a safety sensor SS4, a squib SQ4, and a semiconductor switching device SW4 such as a field effect transistor. The side airbag is typically placed at the door side near the driver's or front passenger's seat, or a side facing the door of the relevant seat.
According to the above airbag apparatus, when another automobile crashes (by any reason) into a door close to the driver's or front passenger's seat of the automobile, safety sensor SS3 or SS4 is closed responding to a relatively minor acceleration, and the squib circuit at the driver's or front passenger's seat is placed in an operable state. And, when the control circuit CC judges that a collision has definitely taken place according to the signals from the accelerometer GS, a signal is sent to the gate of switching device SW3 or SW4 and the switching device SW3 or SW4 is closed. As a result of a current flowing in one of the respective squib circuits, the side airbag at the driver's side or front passenger's side is immediately deployed because of the heating in the squib SQ3 or SQ4, and the relevant occupant is protected from the collision impact caused by a flank collision.
Here, the seating conditions of the passengers are various, and FIG. 14 shows examples thereof. In FIG. 14, seat 1 has sitting section 1a, backrest section 1b, and seat supporting section 1c. A passenger can be seated in any condition as shown using solid lines or dotted lines, or the condition may change from the first state as shown by the solid lines to the second state as shown by the dotted lines.
When a passenger P is seated at the center of seat 1 as shown by the solid lines in FIG. 14, even if a collision occurs against a side of the automobile, the deployment of the side airbag protects the passenger P from the shock caused by the collision. However, when the passenger P is seated on seat 1 leaning against the seat supporting section 1c at the door Dr side as shown by the dotted lines, even if a collision occurs against a side of the automobile, non-deployment of the side airbag may be very desirable.